Machine for separating bark from wood chips



1962 F. G. BLANCHARD 3,0 0, 8

INVEN TOR.

United. States Patent (211cc 3,070,318 MAQHINE FOR? SEPARATING FRQM. WQ D HIB Francis. G. Blanchard, Hopkinton, N.H.,, assignor to Hos! mer. Machine" and Lumber Company, Incorporated, Contoocook, 151.11., a corporation ofNew Hampshire Filed June 6, 1960, Ser. No. 33,985 6' Claims. (Cl. 2 4l-'14) In cutting a log into chips for making wood pulp some of the bark is brokenoif and some remains on the chips. Inasmuch asthe bark degrades the pulp various machines and methods have been devised to separate; the bark from the chips. However none of them has been satisfactory. Some of them do not remove all of the bark, some remove a substantial amount of the chips along withthe bark, somed-amage the chips and some-are prohibitive in cost.

Qbjects of the present invention are to provide amachine for separatingbark from wood chips, which removes substantially all of the bark without damage to thechips, which is effective on a mixture of woodchips, and barkin which the pieces have different characteristics in respect to thickness, moisture con-t'ent, degrees of seasoning, maturity and frozen or unfrozen, which is simple and economical to produce, and which is durable and reliable in use.

In one aspect the machine comprises crushing means having opposed surfaces for. chips and barktherebetween, the surfaces converging towards each other to a minispacing which is less than the thickness of the chips and thence diverging from each other, together with means for removing the bark-wl1ich;adheres to one or both of the surfaces after the surfaces-have been diverged from each other. Preferably-the two surfaces travel at substantially the same linear speed and the latter means comprise scrapers bearing on the surfaces of the pressure means after the surfaces have-- diverged from each other.

In another aspect-one ofsaid surfaces is yielding and the other surface has ridges for'pressing the chips and bark against the yielding surface, thereby to crush the bark without damaging the chips; Preferably the ridged surface is on aroll-andthe ridges extend circumferentially of the roll;

In still another aspectthe machine comprises a pair of opposed rollsone of; which has a yielding surface containing circumferential recesses, and the other of which has relatively rigid circumferential ridges meshing with the recesses, together with means for driving the rolls, preferably approximately the same linear speed, so that bark and chips fed into the crotch between the rolls are yieldingly compressed to crumble and/or cut the bark. Preferably the portions of the ridges which extend into the recesses are tapered, the spacing between rolls is greater between the recesses than at the recesses, and the recesses and ridges are approximately the same width.

In the preferred embodiment the machine comprises a set of juxtaposed rolls having approximately parallel horizontal axes and having a space therebetween which is less than the thickness of the chips, so that the bark is crushed when chips and bark are fed downwardly between the rolls, with a screen beneath the aforesaid space to separate the smaller pieces of chips and bark which fall from the rolls, a second set of rolls to crush said small pieces of bark which pass through the screen, the space between the rolls of the second set being less than the space between rolls of the first set and less than the thickness of the small chips which pass through the aforesaid screen, a third set of rolls one of which has a yielding surface containing circumferential recesses and the other of which has relatively rigid circumferential 3,070,318 Patented Dee. 25, 196-2 ridges-- meshing with: the recesses, means for directing to the third setofrollsthe large pieces. which do not pass: through the aforesaid' screen ands also. the pieces which fall'from the space hetweenthe rolls: of? the sec ond set, means for separately== removing: the bark. which adheres to the aforesaid rolls, and means-for screening the materialwvhich fall'sfromthe space between the-rolls of the third set; The machine should of course have means foradjusting the-"spacing between the rollsof each pair.

Best results are obtainedwhen the mixture of chips and bark has a moisturecontent of-' about fifty percent byweight. Ifthe wood is greenit-may lie-processed after screening out slivers and pieces of wood larger than; a predetermined sizecf chips. If the bark is dry the material should be tempered; as for exampleby-"soaking ;for about thirty- -minu-tes or more inwaterat a temperature of aboutto=200 *F: Under suchconditions the cambium side of-the barkis sticky and the pieces qf-ba-r-k brokenfromthe chips by-ther0lls tend to adhere to the rolls so thatthey carry to the bottomor outer sides of the rolls where they can be removed separately from; chips: which fall from the-space between the rolls,

For the purposeofi illustrationatypical embodiment of; the, invention is shown in theaccompanying drawa ings in which- FI G. lisa diagrammatic-view of a machine;

FIGLZjs-a section on line 2*-2of*FIG. 11; and

FIG. 3-is-a section-on line 3-3-of FIG. 1".

The particular embodiment of the invention chosen for the purpose of illustration comprises a pair-of-'-rolls l; and'2 and a hopper-3 for-feeding chips and bark into the crotchbetween the rolls; Preferably the rollsare made of'steel or other hardmaterial and the periphery of one of the rolls is provided with knurling- 4 to assist in feeding the material downward-1y between the rolls. The space, between the rolls in the plane of their axes should" be less than the thickness of the chips so; that, asthe chips and bark pass between the rolls, the chips are compressed. and the bark is crushed. As stated; above the bark should bemoistso thatrnore' loose pieces-of bark adhere to the rolls; Disposed 'attheouter; lower sides of the rolls are scrapers ,6' and 7-'which scrape oif the bark adhering to the rolls, this bark being diverted to opposite sides'ofthe-machine-byguidesh and 9: For mostpurposes the minimum" spacing between the rolls 1* and2may be of-theorder of fou-r hundredthsof arr-inch:

Disposed below the rolls 1 and 2 is an inclined screen 11 for screening out the coarser material which is diverted to a passageway 12 by means of a guide 13, the smaller pieces of material falling through a chute 14 to a pair of rolls 16 and 17 which are constructed like the rolls 1 and 2 but are spaced closer together, say two hundredths of an inch apart. These rolls are also provided' with scrapers 18 and 19 for removing the bark adhering thereto. The bark scraped from roll 16 is diverted to one side by a guide 21. The bark scraped from roll 17 and the material which does not adhere to either roll falls through a passageway 22 to another pair of rolls 23 and 24. However the bark scraped off by 19 may be deflected by a guide, like guide 9 under roll 2, and discarded.

As shown in FIG. 3 the roll '23 has a covering of rubber or other resilient material and has recesses 26 extending around its periphery. The hardness of the roll should be about 70 durometer. steel or other relatively rigid material and has ridges 27 opposite the recesses 26, the ends of the ridges preferably being tapered as shown in FIG. 3. The ridges 27 should approach close to the recesses 26 and preferably enter The roll 24 is formed of.

the recesses as shown in FIG. 3. While the dimension may vary for different kinds of wood, in a typical example the recesses may be an eighth of an inch deep and a sixteenth of an inch wide, the distance between adjacent recesses may be one-eighth inch, the thickness of the resilient cover on the roll 23 may be one inch, the height of the ridges 27 may be one-quarter inch, the thickness of the ridges may be one-sixteenth inch, the spacing between ridges may be one-eighth inch, and the extent to which the ridges extend into the recesses may be one-sixteenth inch. Owingto the resiliency of the roll 23 the ridges 27 do not cut the wood, although they may make shallow score marks which are barely visible. Fairly good results may be obtained without the recesses 26 in which case the rubber should be more yielding and the ridges 27 may be spaced somewhat from the periphery of rolls 23 or press into the periphery of the rubber covering.

The pieces of bark which adhere to the rolls 23 and 24 are removed from the rolls by scrapers 28 and 29 and diverted to opposite sides of the machine by guides 31 and 32. The material falling from between the rolls is delivered to a rotary screen 33 through a chute 34, the bark passing through the screen as indicated at 36 and the chips passing out of the end of the screen as indicated at 38. a

Means for adjusting the spacing between the rolls is shown diagrammatically at 39, 40 and 41.

It should be understood that the present disclosure is for the purpose of illustration only and that this invention includes all modifications and equivalents which fall within the scope of the appended claims. For example rolls 16 and 17 may be dispensed with and additional pairs of rolls like 23 and 24 may be interposed in series between rolls 23 and 24 and the screen 33.

I claim: i

1. For separating bark from wood chips, a machine comprising a set of juxtaposed rolls having approximately parallel horizontal axes and having a space therebetween set of rolls large pieces which do not pass through said screen and also the pieces which fall from the space between the rolls of said second set, means for separately moving the bark which adheres to said rolls and means for screening the material which falls from the space between the rolls of the third set.

2. For separating bark from wood chips, a machine comprising a pair of opposed rolls, one roll containing circumferential recesses and the other roll having ridges opposed to said recesses, and means for feeding bark and chips into the crotch between the rolls, the sides of said recess being yielding so the bark may be crumbled without damaging the chips.

3. A machine according to claim 2, wherein said ridges are tapered and extend into said recesses.

4. For separating bark from wood chips, the metho which comprises compressing the chips between two moving surfaces which converge toward each other to a minimum spacing which is substantially less than the thickness of the chips and bark so that the bark is crushed but which is large enough to pass the chips without substantial crushing, and separating the crushed bark from the wood.

5. The method according to claim 4, wherein the bark contains enough moisture to adhere to one of said surfaces and is separately removed from the surface.

6. The method according to claim 4 wherein the chips are permitted to fall from said surfaces at one location,

fall from the rolls, a second set of rolls to crush said 1 the bark contains enough moisture to adhere to one of said surfaces and is removed from the surface at another location.

References Cited in the file of this patent UNITED STATES PATENTS 176,176 Guilder Apr. 18, 1876 181,914 Croft Sept. 5, 1876 220,950 Wallace Oct. 28, 1879 313,987 Burckhardt Mar. 17, 1885 409,186 Friend Aug. 20, 1889 673,768 Fleming May 7, 1901 989,421 Reinhardt Apr. 11, 1911 1,631,423 Lucas June 7, 1927 1,722,943 Pettit July 30, 1929 1,753,210 Melville Apr. 8, 1930 2,417,599 Joyce Mar. 18, 1947 2,589,603 Cohen Mar. 18, 1952 2,686,011 Oishi Aug. 10, 1954 2,835,292 Berliner May 20, 1958 OTHER REFERENCES Germany, B 3946IVa/22i, Mar. 10, 1956.

UNITED STATES PATENT OFFICE CERTIFICATE OF CORRECTION Patent Noo 3 070 318 December 25 1962 Francis Ga Blanchard It is hereby certified that error appears in the above numbered patent requiring correction and that the said Letters Patent should read as corrected below.

Column 4 line 4 for" "moving" read removing =0 Signed and sealed this 18th day of June 1963;,

(SEAL) Attest:

ERNEST w. SWIDER DAVID L- LADD Attesting Officer Commissioner of Patents 

